Veiro J A, Khalifah R G, Rowe E S
Biochemistry Department, University of Kansas Medical School, Kansas City 66103.
Biophys J. 1990 Mar;57(3):637-41. doi: 10.1016/S0006-3495(90)82581-9.
We have utilized phosphorus nuclear magnetic resonance, which provides an excellent means of characterizing the physical state of lipids, to investigate the polymorphic phase behavior of pure dielaidoylphosphatidylethanolamine (DEPE). We have observed a sharp isotropic component in the typical bilayer and inverted hexagonal P-31 NMR spectra. This component appears in the spectra of both the bilayer and inverted hexagonal lipid phases after several cycles through the bilayer-to-hexagonal phase transition. The magnitude of the isotropic component increased as a function of the number of cycles through the transition. The appearance of this component was not a function of time at constant temperature, but only a function of the number of cycles through the transition. The isotropic component is stable at all temperatures above the gel-to-liquid crystal transition, but it abruptly disappears when the lipid is cooled below the gel-to-liquid crystal phase transition. It is suggested that this isotropic phase is similar to the isotropic phase observed in dioleoylphosphatidylethanolamine (DOPE) by x-ray diffraction and identified as a cubic phase (Shyamsunder, E., S. M. Gruner, M. W. Tate, D. C. Turner, P. T. C. So, and C. P. S. Tilcock. 1988. Biochemistry. 27:2332-2336).
我们利用磷核磁共振（它提供了一种表征脂质物理状态的极佳方法）来研究纯二油酰磷脂酰乙醇胺（DEPE）的多晶型相行为。我们在典型的双层和反相六角形的P - 31 NMR谱中观察到一个尖锐的各向同性成分。在经历了从双层相到六角相的几次转变循环后，这个成分出现在双层相和反相六角形脂质相的谱图中。各向同性成分的大小随着转变循环次数的增加而增大。该成分的出现不是恒温下时间的函数，而仅仅是转变循环次数的函数。各向同性成分在高于凝胶 - 液晶转变的所有温度下都是稳定的，但当脂质冷却到低于凝胶 - 液晶相转变温度时，它会突然消失。有人认为这个各向同性相类似于通过X射线衍射在二油酰磷脂酰乙醇胺（DOPE）中观察到并被鉴定为立方相的各向同性相（Shyamsunder, E., S. M. Gruner, M. W. Tate, D. C. Turner, P. T. C. So, and C. P. S. Tilcock. 1988. Biochemistry. 27:2332 - 2336）。
